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FSQ CAA Update/Fix

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  • sc02492
    Hi everyone, I spoke to Fred today- he told me that the correct wrench size is 0.035 and confirmed that previous sources stating 0.25mm are incorrect. Today
    Message 1 of 1 , Aug 28, 2007
      Hi everyone,

      I spoke to Fred today- he told me that the correct wrench size is
      0.035" and confirmed that previous sources stating 0.25mm are
      incorrect. Today I adjusted my FSQ CAA and thought that I would post
      the "procedure" here. It was very simple, but I don't know if it
      would always be this easy, so proceed at your own risk.

      The reason for doing this is to remove any play in the CAA, which
      could introduce camera tilt and cause out of round stars in the
      corners. With a heavy, large chip camera, you don't need much tilt to
      cause this effect. In my case, the star elongation did not track with
      camera rotation, which was a clue that it was related to sag
      introduced by the CAA, as opposed to a tilted CCD chip for instance.

      Here's what I did:

      1. Take off the CAA so that it is easy to work with. It simply
      unscrews from the focuser tube (once you lock it down so that it
      doesn't rotate).

      2. There are three tiny screws that hold the silver ring in place.
      Each screw sits inside a hole filled with a thin layer of glue. Fred
      and I hypothesized that this glue is designed to prevent people like
      me from mucking around with the CAA <g>. Actually, it's probably
      there simply to prevent the screws from loosening up over time. The
      glue must be removed in order to insert the hex wrench. I used nail
      polish remover and applied it with a Q-tip over the hole, wiping off
      any excess, and let it sit for about 5 minutes.

      3. Remove the old glue, which is now softened, by inserting a pin
      into each hole to clean it out.

      4. Insert the 0.035" hex wrench (I purchased one at a local
      electronics shop, but you can get one from McMaster Carr) into one of
      the screws- make sure that it sits squarely- you will feel it settle
      in. If you don't remove the glue completely, you will have difficulty
      getting the wrench to sit squarely into the screw head. Loosen the
      screw by turning counterclockwise. It will suddenly "give" and will
      be easy to turn afterwards. You only have to loosen two of the three
      screws to be able to turn the silver ring.

      5. Turn the silver ring clockwise to tighten it. In my case, this
      required less than 1/8 of a full turn. This was sufficient to remove
      any play, and yet still permit rotation of the CAA. If you turn it
      too much, it will cause the CAA to bind up- if that happens just
      loosen it a bit.

      6. Retighten the set screws, and you're done.

      This was a very easy fix. The star elongation in the corners is now
      gone, and I can keep the CAA lock knob loose (in order to use my
      Takometer) without worrying about tilt. I will post a before and
      after image in the next day or two.


      Steve

      Steve Cannistra
      http://www.starrywonders.com
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